During the electro-winning or electro-refining of many metals, oxygen gas may be released at the anode and hydrogen gas may be released at the cathode. Both phenomena reduce the current efficiency, since energy is diverted from production of the metal to production of gas.
The gas is released initially as fine bubbles along the face of the electrodes, and the bubbles rise to the electrolyte surface where they discharge to the atmosphere. This process produces an aerosol mist above the cells with the smaller bubbles imparting more energy to the acid droplets formed when the bubbles burst at the electrolyte surface. This in turn poses a major health hazard to the process operators as well as a corrosion problem for the equipment and the building.
Certain attempts in the past to come to grips with this problem have included installing ventilation systems, plastic screens or sheets provided around the electrodes, covers over the tanks, balls, electrode hoods, and the use of surface active agents in the electrolyte. All of these prior methods involve high maintenance costs and high installation costs, and some involve an increased energy consumption.